Such a light fraction is obtained, for example, from the shredding of scrap vehicles. The shredding of scrap vehicles and similar material flows for material breakdown with the aim of improved material usage has been known for a long time. Scrap body shells, that are first stripped by local scrap vehicle reuse organizations of economically usable parts (generally replacement parts) and unloaded of harmful substances (e.g. by removing operating fluids) are fed to shredder equipment without major pretreatment by shredder operations. In the established method management in carrying out the shredding process, the material mixture obtained is divided up into different fractions.
In the shredder equipment working on the principle of a hammer mill, the scrap body shell is broken into pieces the size of one's fist. Subsequently to the size reduction process, components capable of flying are suctioned off using a suitable suction machine and are segregated via a cyclone separator (the so-called light shredder fraction (SLF)). The remaining air flow is fed to a dust removal. The remaining fraction that is not suctioned off is subsequently split up into a ferromagnetic fraction (so-called shredder scrap (SS)) and a non-ferromagnetic fraction (so-called heavy shredder fraction (SSF)), using a suitable magnetic separator.
The shredder scrap (SS) is used directly as secondary raw material in steel works, the heavy shredder fraction (SSF) is conditioned separately, and separated into metallurgically usable metal fractions and a metal-depleted residual fraction. Beside these residues from the heavy shredder fraction (SSF), the light shredder fraction (SLF) remains as an extremely heterogeneous mixtures of plastics, foamed plastics, rubber, textiles, glass, ceramics, wood, ferrous and nonferrous metals. According to present systems, the so-called shredder residues, thus formed by the light shredder fraction (SLF) and/or the residual fraction from the conditioning of the heavy shredder fraction (SSF) that is not metallurgically usable, are disposed of as waste, as a rule, or burnt in waste incineration plants. In the light of rising legal requirements (such as the EU scrap auto guide lines), rising landfill costs and rising requirements on landfill material, as high a rate of use as possible of all the fractions created in the shredder process would be desirable. Thus, the Scrapped Car Regulation of Apr. 1, 1998 even provides for over 95 wt. % of a scrapped car having to be utilized as of the year 2015. In addition, increased requirements from the EU Scrapped Car Guideline passed in September, 2000 specify that, in scrap car utilization, the proportion of material streams utilizable again as materials and raw materials should be increased to at least 85 wt. %.
Utilization of light shredder fraction (SLF) of a safe quality (materially, for instance, in blast or cupola furnaces or even energetically, for instance, for use as fuel in cement works or power plants) is, according to current knowledge, only possible under ecologically or economically defensible conditions if the shredder residues or the light shredder fraction (SLF) are split up with the aid of suitable conditioning steps into as high-valued, homogeneous subfractions as possible.
European Published Patent Application No. 1 333 931 describes a method for the conditioning in common of shredder fractions in which, among other things, a qualitatively high value or materially or energetically usable lint fraction is able to be produced. In this context, in preprocesses, the light shredder fraction (SLF), the heavy shredder fraction (SSF) and the material flows created in the preprocesses are conditioned and, at least in parts, in a common main process, a raw lint fraction is produced by the segregation of at least one ferromagnetic fraction, an NE metal-containing fraction, a granulate fraction and a sand fraction. The raw-lint fraction thus produced, which is already very homogeneous, is split up in a further refining process by the successive process steps of treating with metal balls, dedusting and density separation into a metal-containing dust fraction, a lint fraction low in dust and metals, and a metallic fraction. The high-value lint fraction produced thereby may be used without a problem for material or energy purposes.
German Published Patent Application No. 102 24 133 describes a method for treating mud, which is supposed to be used for efficient mechanical dehydration in the preliminary stages of a later thermal treatment of the mud. It is proposed, among other things, that one feed in additives to the mud, in the form of a refined lint fraction, according to the method described in European Published Patent Application No. 1 333 931. Furthermore, reference is also made to the possibilities of an additional conditioning of the lint fraction thus refined, which includes the method steps of impact treatment, straining, density separation. The light fraction (lint) obtained from the density separation is combined with the overflow of the straining (also lint) and is submitted to the downstream alternative method steps of size reduction, agglomeration, pelletizing or briquetting. In addition, in the case of agglomerization, it is proposed that the material discharge of the agglomerator be submitted to the additional conditioning stages of sieving out non-agglomerized, lumpy parts, additional FE metal segregation as well as material cooling during pneumatic conveying.
A method is described in German Published Patent Application No. 197 55 629 for conditioning the light shredder fraction from shredder systems, in which the complex light shredder fraction is subdivided by size reduction and separation into the four subfractions: shredder sand (substantially removed inert materials such as glass, sand, dirt), shredder granulate (substantially plastics granulate), metal granulate (substantially of isolated iron, copper and aluminum) and shredder lint (light substances capable of flying), the subfractions being supposed to be so homogeneous that they are able to be fed to a material and/or an energy-producing utilization.
European Published Patent Application No. 1 337 341 describes a method for the joint conditioning of shredder fractions, in which the primary material flows created during the conditioning of the light shredder fraction and the heavy shredder fraction in preprocesses are fed, at least in part, to a common main process for the final conditioning. At least a ferromagnetic fraction, a fraction containing nonferrous metals, a granulate fraction, a sand fraction and a lint fraction are produced as end products. Let it be pointed out that the end products are able to be fed either directly to a material or energetic utilization, or that they may, if necessary, be processed further in additional refinement steps to form usable products of high quality.